The permeability is influenced by environmental factors such as temperature, relative humidity (RH), and surrounding driving factors. Here are some of its important features:
•For every 10 ° C increase in temperature, the transmittance doubles.
•Humidity can cause non Fick behavior of hydrophilic materials (e.g. EVOH getting wet)
•Transmittance is directly proportional to driving force
•Transmittance is inversely proportional to material thickness
Therefore, testing under controlled temperature and relative humidity is crucial for obtaining accurate transmittance results.
The permeability is also influenced by the properties and interactions of polymers and permeants. Some factors include but are not limited to:
•Chemical substituents on the polymer backbone
•Stacking degree, crystallinity, and orientation of molecular chains
•Sensitivity to moisture and other possible interactions with the chain (e.g. EVOH getting wet)
•Penetrating material in contact with polymer surface
•Additives used for manufacturing or modifying polymers
•Polarity of polymers and permeants.